The present invention relates to new and useful improvements in two-stroke cycle gasoline engines, and more particularly to new and useful improvements in exhaust valves for such engines which will delay the opening of the exhaust port during the expansion stroke and, if desired, advance closing of the exhaust port during the compression stroke while, at the same time, fully opening the exhaust port during scavenging of the cylinder. In addition, the present invention also permits varying the opening and closing of the exhaust port relative to the piston position according to engine speed.
It has been known in the past to provide speed-controlled exhaust valves which will remain partially closed at slow speeds of the engine, delaying communication between the combustion chamber and exhaust passage beyond the usual opening of the exhaust port by the piston, and move upwardly, fully exposing the exhaust passage to the combustion chamber through the exhaust port at high engine speeds. Such valves, however, do not provide the advantages of longer expansion and compression strokes while also permitting maximum scavenging.
With the foregoing in mind, a principal object of the present invention is to provide a novel exhaust control valve for two-stroke cycle engines which will vary the exhaust opening according to a selected pattern during each stroke of the piston.
Another object of the present invention is to provide a novel exhaust control valve for two-stroke cycle engines which, in addition to varying the exhaust opening during each cycle, will further change the exhaust opening with changes of engine speed.
A further object of the present invention is to provide a novel reciprocating exhaust control valve driven in timed relation to the piston movement to delay opening of the exhaust passage during the expansion stroke and advance closing of the exhaust passage during the compression stroke, while fully opening the exhaust passage during scavenging.
Still a further object of the present invention is to provide a novel exhaust control valve for two-stroke cycle engines which may be easily incorporated into an engine and will operate reliably and efficiently.